Conventionally, galactoxyloglucan is used as a natural polysaccharide. Galactoxyloglucan includes glucose, xylose, and galactose as constituent sugars, a main chain of which has β-1,4-bonded glucose, and a side chain of which has xylose and galactose bonded to the xylose. Galactoxyloglucan itself is not usually gelled.
Meanwhile, LM pectin is also used as a natural polysaccharide, and, in a solution with LM pectin dissolved in water, when calcium ions are added thereto, carboxy groups are crosslinked with the calcium ions and thereby LM pectin is gelled.
Contrarily, since galactoxyloglucan is a neutral polysaccharide, it is not gelled even if ions such as calcium are added thereto.
Meanwhile, there has been proposed a partial degradation product of the galactose moiety of galactoxyloglucan, which is obtained by partially degrading (partial degradation) to remove a galactose moiety constituting a part of the side chain of galactoxyloglucan using refined β-galactosidase derived from microorganisms (hereinafter also referred to simply as “galactose-partial degradation product” or “partial degradation product”) (see Patent Literatures 1 and 2). When galactose-partial degradation product is mixed with an aqueous solvent, a mixture thereof shows a thermal behavior having a reversed relationship with the thermal behavior of the galactoxyloglucan. Specifically, the galactose-partial degradation product is gelled when heated and solated when cooled so that it shows a thermal behavior in this sol/gel change is reversible. Such a thermal behavior is called reverse thermal gelation characteristics. The galactose-partial degradation product is derived from natural polysaccharides and is not subjected to chemical modification (addition), and therefore is harmless to humans and the environment. Therefore, gel compositions produced using the galactose-partial degradation product can be widely used in foods, cosmetics, pharmaceutical formulations and the like. There have been proposed, as a production method for a gel composition including a galactose-partial degradation product of this kind, a method for producing a gel composition by mixing a cooled aqueous solvent with a galactose-partial degradation product to allow the galactose-partial degradation product to dissolve in the aqueous solvent, and gelling the dissolved solution by heating, and a method for producing a film composition by promoting drying of the produced gel (see Patent Literatures 1 and 2).